At the tail end of the season, the summer of 2023 seems to have another extreme weather event in store for the Mediterranean. After weeks of heat waves, high seawater temperatures, devastating fires and mudslides due to heavy rain, Storm Daniel is now threatening to make landfall in Libya as a hurricane. A ‘medicane’, as such a Mediterranean hurricane is called, is forming in the Gulf of Sidra.
Floods were already reported yesterday in Libya, including in the capital Tripoli, as a result of extreme rain. Streets are also flooded in Misrata in the northwest of the country. Ports, schools and public buildings are forced to remain closed. Many companies are also not opening due to the severe weather.
This morning, Daniel is expected to pass over the northeastern city of Benghazi. It is not yet clear to what extent Daniel, who has already caused enormous damage in Greece as a storm, will move on from Libya to Egypt. Once above land, Daniel will lose strength.
Yesterday, cars had to drive through deep water in Misrata:
This is a relatively rare hurricane that only occurs a few times a year, usually between October and April. During that period the upper air is very cold and there can be a large temperature difference with the sea water. A difference of 57 degrees is required for the formation of a medicane. The current high temperature of the Mediterranean Sea is now causing such a big difference.
Call cold air
“The formation of a medicane is a fairly delicate process, in which a number of factors have to be exactly right for the storm to arise,” explains researcher Nadia Bloemendaal of the KNMI. “First, we need instability. This is often due to a bubble of cold air, usually from the Arctic, ending up above the warm sea water in the Mediterranean Sea.” This instability causes rain and thunderstorms.
There should also be little difference between the wind speed on the ground and high in the air. Meteorologists call this vertical wind shear. “This means that rain and thunderstorms are not blown apart and can continue to intensify,” says Bloemendaal.
The medicanes are smaller than the tropical variants that arise above the much larger oceans and, for example, regularly come ashore in the United States and the Caribbean. Nevertheless, they can cause enormous damage: the Mediterranean is densely populated; the strong winds and heavy precipitation can leave a trail of destruction on the islands and coastal areas on the mainland.
Greece hit earlier
Heavy rainfall in particular can disrupt local society. In 2020, four deaths occurred in Greece when medicane Ianos made landfall. A state of emergency was declared on the islands of Ithaka, Kefalonia and Zakynthos and there was also a lot of damage on the mainland, including to the harvests there. Ianos caused more than 160 million euros in damage.
Also in October 2021, a hurricane hit the Mediterranean. Medicane Apollo brought enormous amounts of rainfall and caused flooding in Tunisia, Algeria, Italy and Malta. In Sicily, 600 millimeters of rain fell locally in three days. For comparison: an average of 855 millimeters falls in De Bilt in an entire year. The total damage: more than 200 million euros.
More severe medications due to climate change
The UN climate panel IPCC previously concluded, based on the available research into medicines, that the number of hurricanes above the Mediterranean Sea will decrease due to climate change, but that due to global warming the hurricanes will be heavier and longer lasting and will bring more precipitation. will bring. The damage caused by medication will therefore increase as a result of climate change.
“The warmer seawater contributes to the intensification of the medicanes, but above all it also makes them ‘wetter’,” explains hurricane expert Bloemendaal. The warmer the seawater is, the more the relatively cold upper air absorbs the warm seawater, causing rain. It’s called convection.
Other processes also play a role in climate change. “The upper air also becomes warmer, which reduces the difference between the surface and high in the atmosphere. The chance of enough instability to form a medicane therefore decreases,” says Bloemendaal. “In addition, wind shear is expected to increase in parts of the Mediterranean, which may also contribute to a decrease in medicanes.”
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